As wireless communication devices flourish, there is a need for higher data rates and spectral efficiency. Multi-carrier systems, where carriers may reside in a single or different bands, can provide higher data rates in wireless communications systems, and have been playing a significant role in a wide variety of wireless standards. In multi-carrier systems, the carriers may be adjacent to each other, or they may be non-adjacent to each other. Non-adjacent carrier allocation means there are frequency gaps among the carriers. Non-adjacent carrier operation may help to increase the data rate in various situations. For example, when operators have scattered spectrum in a single band, or when dynamic spectrum allocation comes into play.